Light emitting device and vehicle display device

ABSTRACT

A light emitting apparatus comprising: a light guiding member that projects light, that is incident on an end face thereof, through a principal plane; and a plurality of light emitting diodes that are optically coupled with the end face, wherein the light guiding member has a protruding surface formed in part of the end face thereof and comprises a first light introducing portion that is formed on the protruding surface and is optically coupled to a first light emitting diode, and a second light introducing portion that is optically coupled to a second light emitting diode and is formed on the rest of the end face, and the first and second light emitting diodes are capable of emitting color-blended light having two or more peaks in the spectrum.  
     The above structure is capable of satisfactorily blending light color and emitting light with high brightness in a very small size.

TECHNICAL FIELD

[0001] The present invention relates to a light emitting apparatus thatprojects light, that is emitted by a light emitting diode, through alight guiding member and, more particularly, to a light emittingapparatus and a vehicle instrument panel display used in vehicles or asthe pointer of various meters.

BACKGROUND ART

[0002] Light emitting apparatuses currently in use include, for example,light bulbs and fluorescent lamps that are used so that meters ofautomobiles and motorcycles can be recognized at night. Light bulbs,however, are not appropriate due to problems related to reliability,power consumption and size. Fluorescent lamps have such problems asancillary devices required for alternating current driving and mercurythat is used inside the lamp and may be released into the atmospherewhen the vehicle is scrapped. Meanwhile a light emitting diode having arelatively simple constitution of single-chip, 2-terminal constructionthat is capable of emitting white light has been developed. Such a lightemitting diode uses an LED chip that is a semiconductor light emittingdevice having high reliability with low power consumption and capable ofbeing designed to be small in size, and a fluorescent substance thatconverts light emitted by the LED chip in at least a part of thespectrum so as to emit blended light such as white light.

[0003] The light emitting diode as described above may be applied to ameter pointer of vehicle or bar-shaped light source as shown in FIG. 6.The apparatus shown in FIG. 6 comprises bullet-shaped light emittingdiodes 602 disposed at an end of a needle-shaped light guiding member601. The light emitting diode comprises an LED chip and a fluorescentsubstance that absorbs light emitted by the LED chip and converts thewavelength thereof. When the light emitting diode is fed with current,blue light emitted by the LED chip and color-blended light produced bythe fluorescent substance that absorbs the blue light emitted by the LEDchip and emits yellow light are introduced into a light guiding member.The light guiding member is covered with a reflecting member except fora surface thereof through which light is emitted, so that light isrepetitively reflected within the light guiding member before beingemitted in a needle-shaped beam through the surface that is not coveredby the reflecting member. By using the needle-shaped light guidingmember of such a construction as a meter pointer, such a light emittingapparatus can be made that is small in size, light in weight, high inreliability and efficiency, and is environment-friendly.

[0004] However, the light emitting apparatus of the constitutiondescribed above cannot meet the requirements of higher brightness andsmaller size that are currently imposed in such a trend that the meterpanel is covered with a filter for decorative purpose. While lightintensity can be increased by increasing the current supplied to thelight emitting apparatus, there is a limitation due to heat dissipation,rated operating current, circuit construction and other factors. Whenthe number of light emitting diodes shown in FIG. 6 is simply increased,on the other hand, larger space is required and color blending betweenthe light emitting diodes becomes a problem. That is, while the lightemitting diode is formed on a semiconductor wafer by MOCVD process orthe like, it is very difficult to achieve uniform light emissioncharacteristic, drive characteristic and other properties among some20,000 pieces of semiconductor light emitting diode that aremanufactured from the same wafer, since the properties are affected bythe flow rate of gas, temperature distribution and other factors.

[0005] As a result, when two or more LED chips are used, there is such aproblem that unevenness in color and/or brightness of light emitted bythe light emitting apparatus through blending of light from theplurality of LED chips leads to lower a yield of production. Selectiveuse of the LED chips also results in a lower yield of production.

[0006] In the case of a light emitting diode that utilizes light emittedby an LED chip and a fluorescent substance that absorbs the lightemitted by the LED chip and converts the wavelength thereof, inparticular, the problems described above become conspicuous togetherwith the problems of light emission characteristic and unevendistribution of the fluorescent substance. These problems are seriousbecause the human eye is capable of perceive a difference in hue moredistinctly in white region.

DISCLOSURE OF THE INVENTION

[0007] An object of the present invention is to provide a light emittingapparatus capable of satisfactorily blending light color and emittinglight with high brightness with a small construction, and a vehicleinstrument panel display.

[0008] The present invention provides a light emitting apparatuscomprising a light guiding member that projects light, that is incidenton an end face thereof, through a principal plane and a plurality oflight emitting diodes that are optically coupled with the end face,wherein the light guiding member has a protruding surface formed in partof the end face thereof and comprises a first light introducing portionthat is formed on the protruding surface and is optically coupled to afirst light emitting diode, and a second light introducing portion thatis optically coupled to a second light emitting diode and is formed onthe rest of the end face.

[0009] The constitution described above produces a light emittingapparatus capable of satisfactorily blending light colors and emittinglight with high brightness.

[0010] In the present invention, the light guiding member preferably hasa part of surface protruding on the side of the principal plane thatemits light or on the side opposing the principal plane.

[0011] Such a constitution described above produces a light emittingapparatus capable of satisfactorily blending light colors and emittinglight with high brightness.

[0012] Also in the present invention, the first light emitting diode andthe second light emitting diode are preferably surface-mounted lightemitting diodes with light emitting portion of the first light emittingdiode being higher than that of the second light emitting diode.

[0013] In this constitution, since the portion of the light emittingplane of the first light emitting diode where the emitted light isobserved is higher than the second light emitting diode, all the lightemitted by the first light emitting diode is introduced into the lightguiding member without being blocked by the second light emitting diode.Therefore, a light emitting apparatus of high brightness can be made.

[0014] The present invention also provides a light emitting apparatuscomprising a light guiding member that has a distal end, an end faceopposing the distal end, and a principal plane located between theformer two so as to project the light incident on the end face throughthe principal plane, and at least first and second light emitting diodesoptically connected to the end face of the light guiding member, whereinthe end face of the light guiding member is made in such a structurethat the optical path over which light propagates through the lightguiding member is different in length depending on which of the lightemitting diodes emits the light.

[0015] Such a constitution described above produces a light emittingapparatus capable of satisfactorily blending light colors and emittinglight with high brightness.

[0016] In the present invention, the light guiding member has a shape ofplate having the end face and an end face opposing the former end face,while the end face of the light guiding member has two portionscorresponding to the first and second light emitting diodes with theoptical path between the first end face portion and the end face is madelonger than the optical path between the other end face portion and theend face.

[0017] Such a constitution described above produces a light emittingapparatus capable of satisfactorily blending light colors and emittinglight with high brightness.

[0018] Also in the present invention, the end face of the light guidingmember is preferably made in a stepped structure having such aprotruding surface as the one end face portion protrudes beyond theaxial direction of the light guiding member with respect to the otherend face portion.

[0019] Such a constitution described above produces a light emittingapparatus capable of satisfactorily blending light color and emittinglight with high brightness.

[0020] Also in the present invention, the stepped structure of the lightguiding member is preferably disposed in a direction perpendicular orparallel to the axial direction between the distal end and the end faceof the light guiding member.

[0021] Such a constitution described above produces a light emittingapparatus capable of satisfactorily blending light color and emittinglight with high brightness.

[0022] Also in the present invention, the protruding surface of thelight guiding member is preferably located outside the visible region ofthe light guiding member.

[0023] Such a constitution described above produces a light emittingapparatus capable of satisfactorily blending light color and emittinglight with high brightness.

[0024] Also in the present invention, the first and second lightemitting diodes are preferably capable of emitting color-blended lighthaving two or more peaks in the spectrum.

[0025] Such a constitution described above produces a light emittingapparatus capable of satisfactorily blending light color and emittinglight with high brightness.

[0026] Also in the present invention, the light emitting apparatus ispreferably an instrument meter pointer.

[0027] This makes it possible to make an instrument meter pointer havinghigh brightness.

[0028] Also in the present invention, the light emitting apparatuspreferably has a substrate whereon the light emitting diode and circuitelements are mounted.

[0029] Thus the light emitting apparatus can effectively utilize thespace.

[0030] The present invention also provides a vehicle instrument paneldisplay comprising any one of the light emitting apparatus describedabove as a meter pointer of an instrument panel installed in a vehicle.

[0031] Thus the meter pointer for vehicles capable of satisfactorilyblending light color and emitting light with high brightness can bemade.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032]FIG. 1A is a schematic plan view explanatory of the constitutionof a light emitting apparatus according to the present invention, andFIG. 1B is a schematic sectional view thereof.

[0033]FIG. 2 is a schematic plan view of a meter pointer that uses alight guiding member of the present invention.

[0034]FIG. 3B is a schematic sectional view of a light emittingapparatus explanatory of the constitution according to the presentinvention, while FIG. 3A and FIG. 3C are schematic sectional views of alight emitting apparatus shown for comparison with the present invention

[0035]FIG. 4 is a schematic perspective view of a first light emittingdiode optically coupled with a first light introducing portion that is aprotruding portion.

[0036]FIG. 5 is a schematic perspective view of a second light emittingdiode optically coupled with a second light introducing portion.

[0037]FIG. 6 is a schematic plan view showing the constitution of aneedle-shaped light guiding member shown for comparison with the presentinvention.

[0038]FIG. 7 is a schematic diagram showing an embodiment of the presentinvention.

[0039]FIG. 8 is a schematic diagram showing an embodiment of the presentinvention.

[0040]FIG. 9 is a schematic diagram showing an embodiment of the presentinvention.

[0041]FIG. 10 is a schematic diagram showing an embodiment of thepresent invention.

[0042]FIG. 11 is a schematic diagram showing an embodiment of thepresent invention.

[0043]FIG. 12 is a schematic diagram showing an embodiment of thepresent invention.

[0044]FIG. 13 is a schematic diagram showing an embodiment of thepresent invention.

[0045]FIG. 14 is a schematic diagram showing an embodiment of thepresent invention.

[0046]FIG. 15 is a schematic diagram showing an embodiment of thepresent invention.

[0047]FIG. 16 is a schematic diagram showing an embodiment of thepresent invention.

[0048]FIG. 17 is a schematic diagram showing an embodiment of thepresent invention.

[0049]FIG. 18 is a schematic diagram showing an embodiment of thepresent invention.

[0050]FIG. 19 is a schematic diagram showing an embodiment of thepresent invention.

[0051]FIG. 20 is a schematic diagram showing an embodiment of thepresent invention.

[0052]FIG. 21 is a schematic diagram showing an embodiment of thepresent invention.

[0053]FIG. 22 is a schematic diagram showing an embodiment of thepresent invention.

[0054]FIG. 23 is a schematic diagram showing an embodiment of thepresent invention.

[0055]FIG. 24 is a schematic diagram showing an embodiment of thepresent invention.

[0056]FIG. 25 is a schematic diagram showing an embodiment of thepresent invention.

[0057]FIG. 26 is a schematic diagram showing an embodiment of thepresent invention.

[0058]FIG. 27 is a schematic diagram showing an embodiment of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0059] The present inventors conducted various experiments and completedthe present invention upon finding that a light emitting apparatus thathas high color-blending performance and high efficiency of utilizinglight and is suitable for mass production can be made, by designing thearrangement of two or more light emitting diodes and a light guidingmember in a particular construction.

[0060] Now a needle-shaped light emitting apparatus shown in theschematic sectional view of FIG. 3B will be described below. FIG. 3A andFIG. 3C show light emitting apparatuses for comparison with the presentinvention. The light emitting apparatuses shown in FIG. 3A and FIG. 3Cintroduce light emitted by two light emitting diodes 332 that aredisposed one above another on a flat end face of the needle-shaped lightguiding member. In FIG. 3A, light emitted by each of the light emittingdiodes 332 spreads from the light introducing portion and thereforeuniform light intensity distribution cannot be achieved until the lightcovers the thickness of the light guiding member 301, thus resultingpoor color blending performance when the entire region is utilized. Withthe structure shown in FIG. 3C, on the other hand, although a region ofuniform color blending can be secured by increasing the length of thelight guiding member 301, dead space increases and more light isdiffused and absorbed in the light guiding member 301 resulting in lowerbrightness of light emission. Although the light guiding member 301transmits light, the light is absorbed therein while being reflectedrepetitively and diffused, and therefore a slight increase in the lengthresults in a sharp decrease in brightness. This means that colorblending performance and brightness of emitted light are trade-off foreach other in this constitution.

[0061] According to the present invention, as shown in FIG. 3B, a stepis formed in the light introducing portions that introduce light from aplurality of light emitting diodes into the light guiding member 301.This structure makes it possible to achieve both good color blendingperformance and high brightness of emitted light that have otherwisebeen trade-offs. That is, as will be understood from FIG. 3B, it ispresumably because a difference is given to the optical path length inthe light guiding member 301 to make a functionally separated structure,so that light emitted by the light emitting diode 322 that travels overa shorter length in the light guiding member 301 is effectively utilizedso as to achieve high brightness, while light emitted by the lightemitting diode 312 that travels over a longer length in the lightguiding member 301 is utilized to improve the color blending performancein a range X from the end face to the visible range of the light guidingmember 301. It is assumed that such a structure enables it to eliminatethe dead space and emit light with higher brightness than that achievedby the light guiding member that has a flat light introducing portion.Now various constitutions employed in the present invention will bedescribed in detail below.

[0062] (Light Guiding Member 301)

[0063] The light guiding member used in the present invention receiveslight emitted by a plurality of light emitting diodes and emits thelight in a beam of desired shape. The light guiding member may be formedfrom materials that transmit light and can be easily formed, such aspolycarbonate resin, acrylic resin, amorphous polyolefin resin andpolystyrene resin. Depending on the application, various inorganicmaterials such as glass can be used in addition to organic materialssuch as resin. The light guiding member may have two or more lightintroducing portions formed at the end thereof. The light introducingportion of the present invention has a second light introducing portionof a shorter optical path over which light propagates through the lightguiding member and a first light introducing portion of longer opticalpath over which light propagates through the light guiding member thanthe second light introducing portion. Preferably disposed on the firstand second light introducing portions are light emitting diodes thatemit light with directivity. In order to emit light uniformly from lightemission observing plane of the light guiding member, a light diffusionsheet or a prism sheet may be provided on the light emission observingplane or on the surface opposing thereto, or a micro lens, prism orconstricted portion may be provided on the light emission observingplane of the light guiding member. The light guiding member may also beformed in such a shape as a part thereof protrudes in the principalplane from which light is emitted, namely the light emission observingplane, or in a surface opposing the principal plane. Such a structuremakes it possible to improve the color blending performance and achievelight emitting apparatus of high brightness.

[0064] Moreover, a diffusion agent may be included in the light guidingmember so as to improve the uniformity of light emission, or a coloringagent may be included so as to emit light of a desired color. Thediffusion agent or the coloring agent may be included in the lightguiding member with either uniform distribution or graded distribution.The diffusion agent may be formed from acrylic resin, polycarbonateresin, amorphous polyolefin resin, polymethylene pentene resin or thelike. The coloring agent may be any proper pigment or dye, whilefluorescent dye or fluorescent pigment may also be used.

[0065] The light introducing portion of the light guiding member may beformed in a flat surface or, as shown in FIGS. 26A and 26B, in such ashape as concave 271 (FIG. 26A), groove, notch 272 (FIG. 26B) orconstriction so as to diffuse the light emitted by the light emittingdiode 312 more efficiently. In the present invention, since two or morelight emitting diodes can be made with different angles of directivity,the light introducing portion may be formed in different shapesaccordingly. In a convex light introducing portion that brings aboutlonger optical path, in particular, the notch is made smaller so as toimprove the directivity, while the light introducing portion at thebottom that provides shorter optical path than the convex portion may beformed so as to cause lower directivity, thereby to further improve thebrightness of emitted light and color blending performance. When thesurface area is increased in the convex light introducing portion thatbrings about longer optical path and surface area is decreased in thelight introducing portion at the bottom that provides shorter opticalpath than the convex portion, brightness of emitted light and colorblending performance can be further improved. The surface that opposesthe light emission observing plane of he light guiding member may alsobe formed into prism. For example, a train of prisms (FIG. 11) of jaggedconfiguration 901 having triangular cross section may be formed inparallel, and jagged configuration 902 of smaller ups and downs may alsobe formed on the side of the concave or convex of the jaggedconfiguration 901 (FIG. 11). The train of prisms causes the lightemitted by the light emitting diode to reflect or scatter on a side face901 a of the train of prisms as shown in FIG. 11, and diffracted by aside face 903 a of the train of prisms 903 provided on the cover 201 soas to be directed toward a translucent panel 200, thus resulting inimproved efficiency of extracting light from the light emittingapparatus.

[0066] It is preferable to form a shape of an acute angle at the endface of the light guiding member (904 in FIG. 1A) that opposes to thelight introducing surface of the light emitting diode, in order toimprove the efficiency of utilizing light by efficiently reflectinglight emitted by the light emitting diode, the acute angle being morepreferably in a range from 75 to 105 degrees, and most preferably rightangles.

[0067] (Light Emitting Diodes 312, 322)

[0068] Various types of light emitting diode can be used in the presentinvention as long as light can be efficiently introduced into the lightguiding member. For example, SMD (surface-emitting type) type lightemitting diode or bullet-shaped light emitting diode may be used. Alsoan LED chip that is a bare light emitting element may be used as thelight emitting apparatus. For the first light emitting diode and thesecond light emitting diode, those capable of emitting color-blendedlight having two or more peaks in the spectrum may be used, or thosecapable of emitting single-color light having one peak in the spectrummay be used, or those of different types may be used in combination.

[0069] Materials for the light emitting device may be semiconductormaterials such as BN, SiC, ZnSe, GaN, InGaN, InAlGaN, AlGaN, BalGaN orBInAlGaN. These elements with an impurity element such as Si or Zn addedthereto may be used as the light emission center. Structure ofsemiconductor may be homo-structure, hetero-structure or doublehetero-structure that may have MIS junction, PIN junction or pnjunction. Wavelength of the emitted light may be selected by changingthe materials and/or mix proportion of the semiconductor. Output powermay be increased by forming the semiconductor active layer in a thinfilm of single quantum well structure or multiple quantum well structurethat generates quantum effect.

[0070] The light emitting device that emits color-blended light such aswhite light by the light emitting diode using a fluorescent substance ispreferably a nitride semiconductor (for example, nitride semiconductorincluding Al and Ga or nitride semiconductor including In and Ga havingcomposition of Inl_(x)Al_(y)Ga_(1-X-Y)N, 0≦X, 0≦Y, X+Y≦1).

[0071] When nitride semiconductor is used, substrate for thesemiconductor is preferably made of such material as sapphire, spinel,SiC, Si, ZnO, GaAs or GaN. In order to form the nitride semiconductor ofgood crystallinity favorably in mass production, sapphire substrate ispreferably used. The nitride semiconductor is formed on the sapphiresubstrate by such a process as HVPE or MOCVD. A buffer layer made of amaterial that enables it to grow an amorphous crystal at a lowtemperature such as GaN, AlN or GaAlN is formed on the sapphiresubstrate, and the nitride semiconductor that has pn junction is formedthereon.

[0072] A light emitting device made of a nitride semiconductor having pnjunction that is capable of efficiently emitting light in ultravioletregion may be made by forming stripe of SiO₂ on the buffer layersubstantially at right angles to the orientation flat surface of thesapphire substrate. GaN is grown on the stripe through ELOG (EpitaxialLateral Over Grows GaN) by the HVPE process. Then a doublehetero-junction structure may be constituted by forming a first contactlayer from n-type gallium nitride, a first cladding layer from n-typealuminum gallium nitride, an active layer of multiple quantum wellstructure comprising a plurality of well layers of n-type indiumaluminum gallium nitride, and barrier layers from n-type aluminumgallium nitride stacked one on another, a second cladding layer ofp-type aluminum gallium nitride, and a second contact layer of p-typegallium nitride by the MOCVD process.

[0073] The nitride semiconductor shows n-type conductivity when notdoped with an impurity. In order to form a desired n-type nitridesemiconductor for such a purpose as improving the efficiency of lightemission or the like, it is preferable to introduce an n-type dopantsuch as Si, Ge, Se, Te or C. In order to form a p-type nitridesemiconductor, it is preferable to introduce a p-type dopant such as Zn,Mg, Be, Ca, Sr or Ba. Since a nitride semiconductor does not easily turninto p-type simply by doping with a p-type dopant, it is desired todecrease the resistance by heating in a furnace or irradiating withplasma after introducing the p-type dopant. When the sapphire substrateis not taken, the p-type layer is etched down to the surface of thefirst contact layer so as to expose the contact layer. After formingelectrodes on the contact layers, the semiconductor wafer is cut intochips thereby making the light emitting devices made of the nitridesemiconductor.

[0074] For the fluorescent substance, one that can emit lightefficiently by the spectrum emitted from the semiconductor lightemitting device, such as YAG: Ce fluorescent substance or a derivativeof perylene is used in case the light emitting device emits blue visiblelight. When the light emitting device emits ultraviolet ray, such amaterial may be used as alkali earth metal halogen apatite fluorescentsubstance including at least Mn and/or Cl that is activated with Eu. Byproviding such a fluorescent substance on the LED chip, the lightemitting diode capable of emitting white light can be formed. Accordingto the present invention, a first SMD type light emitting diode havingthickness substantially equal to the thickness of the light guidingmember is disposed on the convex-shaped light introducing portion thatprovides longer optical path, and a second SMD type light emitting diodethat can be accommodated on the thinner light guiding member is disposedon the light introducing portion located at the bottom that providesshorter optical path than that of the convex portion. This constructionenables it to efficiently utilize the space of the light emitting diodesand can be disposed on the substrate without making any adjustment tothe electrodes of the SMD type light emitting diodes.

[0075] (Translucent Panel 200)

[0076] The translucent panel 200 of this embodiment is a translucentmember disposed on the cover 201. As a result, light propagating throughthe light guiding member 301 is observed through the translucent panel200.

[0077] The translucent panel 200 is made of a material that has highlight transmissivity and high moldability such as polycarbonate resin,acrylic resin, amorphous polyolefin resin and polystyrene resin.Depending on the application, various inorganic materials such as glasscan be used in addition to organic materials such as resin. Thetranslucent panel 200 is molded into a desired shape by injectionmolding from a material as described above.

[0078] (Cover 201)

[0079] The cover 201 of this embodiment is a translucent member disposedon the light guiding member 301.

[0080] The cover 201 is made of a material that has high lighttransmissivity and high moldability such as polycarbonate resin, acrylicresin, amorphous polyolefin resin and polystyrene resin. Depending onthe application, various inorganic materials such as glass can be usedin addition to organic materials such as resin. The cover 201 is moldedinto a desired shape by injection molding from a material as describedabove.

[0081] Since the cover 201 used in this embodiment can be processed toform prism on the surface that opposes to the light guiding member 301,the efficiency of extracting light in the direction of light emissionobserving plane can be improved with a relatively simple constructionwithout the necessity to provide a lens sheet or diffusion sheet betweenthe light guiding member 301 and the cover 201. The prisms of thisembodiment are formed by disposing train of prisms 903 (FIG. 11) ofjagged configuration having triangular cross section. The cover 201 ofsuch a configuration as described above is formed by injection moldingusing a die that has a shape of the train of prisms having triangularcross sections.

[0082] (Frame Member)

[0083] The frame member of this embodiment comprises an upper frame 204and a lower frame 202. The lower frame 202 is a member whereon areflecting member 303, a light guiding member 101 and a substrate 103are mounted. The upper frame 204 is a member that can be fitted withoutgap to the lower frame 202 so as to cover the reflecting member 303, thelight guiding member 101 and the substrate 103 that are mounted on thelower frame 202.

[0084] The frame member may be made of a material that has highmoldability such as polycarbonate resin, acrylic resin, amorphouspolyolefin resin, polystyrene resin or polypropylene resin. The framemember is molded into a desired shape by injection molding from amaterial as described above.

[0085] Of the surfaces of the frame members, the surface that faces theinside of the light emitting apparatus and receives the light from thelight emitting diode may be coated with metal plating or a metal filmsuch as silver or aluminum formed by vapor deposition. This makes itpossible to make the light emitting apparatus that emits light withhigher brightness relatively easily using less parts without using areflector sheet or a reflecting member.

[0086] Light emitting apparatus that emits light with higher brightnessmay also be made relatively easily using less parts without employingsuch process as metal plating or vapor deposition, by forming the framemembers of high reflectivity material.

[0087] Furthermore, the upper frame 204 or the lower frame 202 may bemolded with two colors. For example, the upper frame 204 may be formedfrom a white resin on the inside and a black resin on the outsidethereof. Alternatively, the frame may be formed from a white resin thatis then covered with a black coating on the outside. Light emittingapparatus that emits light with higher brightness can be made with sucha construction.

[0088] (Reflecting Member 303)

[0089] The reflecting member 303 is used to efficiently reflect thelight that is received from the light guiding member 301 and project itthrough the light emission observing plane. In order to efficiently emitthe light from the light guiding member 301 through the light emissionobserving plane, it is preferable to cover the light guiding member witha reflecting member except for the light emission observing plane andthe light introducing portion. The reflecting member may be providedeither by vapor deposition of a metal such as silver on the lightguiding member 301, or by bonding a thin sheet. When the reflectingmember is bonded onto the light guiding member 301, it is preferable touse an acrylic-based or silicon-based adhesive that has hightransparency, in order to have the light emitted by the LED chip reachthe reflecting member without loss and have the reflected light transmitto the light emission observing plane without loss. The light emitted bythe LED chip can be extracted efficiently by covering the light guidingmember with a resin sheet that includes a reflecting material such astitanium oxide, barium titanate, barium sulfide or aluminum oxide addedthereto, or a mirror-like reflector sheet made of a film coated withsilver, aluminum or the like by vapor deposition.

[0090] (Embodiment 1)

[0091]FIG. 2 shows a meter pointer that uses the light guiding member ofthe present invention, FIG. 1A being a plan view thereof showing theconstitution and FIG. 1B being a schematic sectional view of the presentinvention. According to the present invention, the light guiding member301 was formed by injection molding using a hopper of acrylic resin. Inthe die used in the injection molding, one end face of the needle-shapedlight guiding member is formed into end face 904 with an acute angle(about 90 degrees) when viewed from the plane, and the other end face isformed to be wider than the former end face so as to optically couplewith the light emitting surface of the light emitting diode. By formingthe end face with an acute angle (about 90 degrees) in the plan and/orsectional view, light incident on the end face after transmittingthrough the light guiding member is reflected on the side face thatforms the end face so as to be directed toward the inside of the lightguiding member and the reflected light is further reflected on the innerwall of the light guiding member so as to be directed toward the lightemission observing plane, thereby improving the efficiency of the lightemitting apparatus to extract light.

[0092] The light guiding member 301 has a protruding first lightintroducing portion formed on the end face thereof to be opticallyconnected to the light emitting diode 312 and a second light introducingportion formed so as to provide shorter optical path than that of thefirst light introducing portion. Surface area of the first lightintroducing portion of the light guiding member 301 is made large andsurface area of the second light introducing portion is made smallerthan the first light introducing portion. Specifically, the rod-shapedlight guiding member 301 of nearly 50 mm in length has the lightintroducing portions disposed one above the other, so that the convexlight introducing portion protrudes beyond the second light introducingportion by about 2 mm. One end face of the light guiding member is about1 mm thick and the first light introducing portion that is the other endface is about 1.7 mm thick. The second light introducing portion isabout 0.3 mm thick.

[0093] Space can be efficiently utilized by mounting the SMD type lightemitting diode 322 shown in FIG. 5 that is less than 2 mm in length andless than 1.3 mm in thickness on the protruding portion of the lightguiding member 301, and mounting the SMD type light emitting diode 312shown in FIG. 4 that is less than 3 mm in thickness and has a lightemitting plane at a position corresponding to the first lightintroducing portion. The SMD type light emitting diodes 312, 322 can bemade by disposing ones that have been formed beforehand by flowsoldering or the like on a glass epoxy substrate whereon an electricallyconductive pattern has been formed. Each of the light emitting diodes312, 322 is made in the form of SMD type light emitting diode thatcomprises an LED chip made of a nitride semiconductor that is capable ofemitting blue light, and a resin including YAG: Ce fluorescent substancethat is excited by the blue light emitted from the LED chip so as toemit light of yellow, namely the complementary color. In the lightemitting surface of the first light emitting diode 312, minimum heightof a visible emitting portion from the substrate 103 can be made largerthan the maximum height (thickness) of the second light emitting diode322. With this construction, a light emitting apparatus of highbrightness can be made since light emitted from the first light emittingdiode 312 enters the light guiding member 301 without being blocked bythe second light emitting diode 322 that is located ahead in thedirection of propagation.

[0094] A reflector made of acrylic resin including barium titanate wasbonded onto the molded light guiding member via epoxy resin used as atransparent adhesive. The reflector is provided except for the principalplane from which light is extracted from the light guiding member andthe end face where light of the light guiding member is introduced. FIG.9 is a schematic sectional view along line A-A′ in. FIG. 7 or FIG. 8. Asshown in FIG. 9, component parts including the translucent panel 200,the cover 201, the light guiding member 101, the reflecting member 303,the upper light transmitting frame member 204 and the lower frame member202 are assembled without gap between the parts. Leakage of light fromthe light emitting apparatus can be minimized by assembling in this way.

[0095] When current is supplied to the light emitting diodes 312, 322,white light enters the light guiding member through the end facethereof, causing planar emission of light from the principal plane ofthe light guiding member. The planar light emission source thus made hashigh color blending performance and high brightness.

[0096] (Embodiment 2)

[0097]FIG. 7 is a schematic sectional view of this embodiment. Similarlyto the first embodiment, the light guiding member 301 has a convex firstlight introducing portion formed on the end face thereof to be opticallyconnected to the light emitting diode 312 and a second light introducingportion formed so as to provide shorter optical path than that of thefirst light introducing portion. Surface area of the first lightintroducing portion of the light guiding member 301 is made large andsurface area of the second light introducing portion is made smallerthan the first light introducing portion. Specifically, the rod-shapedlight guiding member 301 of about 50 mm in length has the lightintroducing portions disposed one above the other, so that the convexlight introducing portion protrudes beyond the second light introducingportion by about 2 mm. One end face of the light guiding member 301 isabout 1.0 mm thick and the first light introducing portion that is theother end face is about 1.7 mm thick. The second light introducingportion is about 0.3 mm thick. The substrate is about 0.4 mm thick. Thesubstrate is coated with metal plating such as silver to make a lightreflecting surface. Providing the silver plating makes it possible toreflect the light emitted by the light emitting diodes 312, 322 in thedirection of the light guiding member with a high reflectivity.

[0098] As shown in FIG. 7, the glass epoxy substrate 103 described aboveis placed on the top surface of the protruding portion of the lightguiding member 301, and the SMD type light emitting diode 322 shown inFIG. 5 that is less than about 2.0 mm in length and less than about 1.3mm in thickness is disposed on the glass epoxy substrate on the side ofthe second light introducing portion. In addition, the SMD type lightemitting diode 312 shown in FIG. 4 that is less than about 3 mm inthickness and has a light emitting plane at a position corresponding tothe first light introducing portion is placed. The SMD type lightemitting diodes 312, 322 may also be constituted by disposing ones thathave been formed beforehand by flow soldering or the like on the glassepoxy substrate whereon an electrically conductive pattern has beenformed. The first light emitting diode 312 and the second light emittingdiode 322 are disposed with a space of about 1.0 to 2.0 mm kepttherebetween. This configuration makes it possible to minimize thethermal influence on the characteristics of the light emitting diodes312, 322, since heat generated by the light emitting diodes 312, 322 isdissipated through different paths.

[0099] The light emitting apparatus was made similarly to the firstembodiment, except for the variations described above. When current issupplied to the light emitting diodes 312, 322, white light enters thelight guiding member through the end face thereof, causing planaremission of light from the principal plane of the light guiding member.The planar light emission source thus made has high color blendingperformance and high brightness.

[0100] (Embodiment 3)

[0101]FIG. 8 is a schematic plan view of this embodiment. As shown inFIG. 8, the light guiding member 301 has a convex first lightintroducing portion formed on the end face thereof to be opticallyconnected to the light emitting diode 312 and a second light introducingportion formed so as to provide shorter optical path than that of theconvex portion. The surface where the substrate is placed, among thesurfaces formed by the convex portion, is formed to be perpendicular tothe light emission observing plane of the light emitting apparatus.Surface area of the first light introducing portion of the light guidingmember 301 is made large and surface area of the second lightintroducing portion is made smaller than the first light introducingportion. Specifically, the rod-shaped light guiding member 301 of about50 mm in length has the light introducing portions disposed one abovethe other, so that the convex light introducing portion protrudes beyondthe second light introducing portion by about 2 mm. One end face of thelight guiding member is about 1 mm thick and the first light introducingportion that is the other end face is about 1.7 mm thick. The secondlight introducing portion is about 0.3 mm thick. The substrate is about0.4 mm thick, and is placed perpendicular to the light emissionobserving plane of the light emitting apparatus. The first lightemitting diode 312 and the second light emitting diode 322 are disposedwith a space of about 1.0 to 2.0 mm kept therebetween. Thisconfiguration makes it possible to minimize the thermal influence on thecharacteristics of the light emitting diodes 312, 322, since heatgenerated by the light emitting diodes 312, 322 is dissipated throughdifferent paths.

[0102] The light emitting apparatus was made similarly to the secondembodiment, except for the variations described above. When current issupplied to the light emitting diodes 312, 322, white light enters thelight guiding member through the end face thereof, thereby causingplanar emission of light from the principal plane of the light guidingmember. The planar light emission source thus made has high colorblending performance and high brightness.

[0103] (Embodiment 4)

[0104]FIG. 11 is a schematic sectional view of this embodiment. Thecover 201 processed to form prisms is placed on the light guidingmember, and the light transmitting panel 200 is placed on the cover 201.The light guiding member has, disposed on at least one of the principalplane and the surface that opposes the principal plane, first prism 901having linear configuration with triangular cross section parallel tothe side face of the light guiding member, and a second prism 902 thatis smaller than the first prisms and is disposed between the pluralityof first prisms.

[0105] The light emitting apparatus was made similarly to the firstthrough fourth embodiments, except for the variations described above.The constitution of this embodiment makes it possible to improve theefficiency of extracting light in the direction of the light emissionobserving plane since the light that has transmitted through the lightguiding member 301 is diffracted by the prism so as to change thedirection of propagation to the direction of the light emissionobserving plane and emerge out of the light emitting apparatus.

[0106] (Embodiment 5)

[0107]FIG. 10 is a schematic plan view of this embodiment. The lightguiding member 301 has a convex first light introducing portion formedon the end face thereof to be optically connected to the light emittingdiode 312 and a second light introducing portion formed so as to provideshorter optical path than that of the convex portion. Prisms 905 similarto the fourth embodiment are formed on the end face whereon the firstlight introducing portion is formed and on the end face whereon thesecond light introducing portion is formed, except for the end facesthat make contact with the light emitting diodes 312, 322. With thisconstitution, light reflected on the distal end and on the side face ofthe light guiding member 301 is reflected also on the end face whereonthe prisms are formed, thereby improving the efficiency of the lightemitting apparatus to extract light.

[0108] (Embodiment 6)

[0109]FIG. 18 is a schematic plan view of this embodiment. The lightemitting apparatus is made similarly to the other embodiments except forfusing the distal end of the light guiding member to the inner surfaceof the frame member that covers the distal end of the light guidingmember, without protruding from the outer surface of the light emittingapparatus. With this construction, light emitted from the distal end ofthe light guiding member can be prevented from leaking through theexternal wall surface of the light emitting apparatus.

[0110] (Embodiment 7)

[0111]FIG. 12 is a schematic sectional view of this embodiment. The endface located on the side of the light guiding member 301 whereon thelight guiding member is optically connected to the light emitting diodeis formed to face the light emission observing plane 704, namely towardthe translucent panel 200. Also formed on the end face are the firstlight introducing portion that is convex and the second lightintroducing portion that provides shorter optical path than that of theconvex portion, similarly to the first embodiment. The light reflectingsurface 701 is formed on part of the light guiding member with an angleto the light emission observing plane and the end face. With thisconstitution, light emitted from the light emitting diodes 312, 322 isreflected on the light reflecting surface 701, that is incident on thesurface 703 that opposes to the light emission observing plane, isdirected toward the light emission observing plane 704 and emerges fromthe light emitting apparatus.

[0112] According to this embodiment, light emitting apparatus that iscapable of both satisfactorily blending light color and improving thebrightness of light emission and can be made very small can be made byutilizing the reflection in the light guiding member.

[0113] (Embodiment 8)

[0114]FIG. 13 is a plan view showing the embodiment where the lightemitting apparatus of the present invention is used for a meter pointer.FIG. 14 is a sectional view of the pointer. A part of the end portion ofthe light guiding member 301 protrudes with the first light introducingportion and the second light introducing portion being formed thereon.Mounted on the first light introducing portion and the second lightintroducing portion are the first light emitting diode 312 and thesecond light emitting diode 322, respectively. The substrate 103 whereonthe first light emitting diode 312 and the second light emitting diode322 are mounted on the same side thereof is placed on the side oppositeto the light emission observing plane, namely on the side of shaft 702of the pointer, and is connected by soldering with a lead electrode 710that supplies power through connection with outside electrode.

[0115]FIG. 9 is a schematic sectional view of the pointer of thisembodiment. As shown in FIG. 9, component parts including the cover 201,the light guiding member 101, the reflecting member 303, the upper framemember 204 and the lower frame member 202 are assembled without gapbetween the parts. Lower side portion of the upper frame member 204 ismade with thinner wall thickness so that, after fitting the cover 201,the light guiding member 301 and the reflecting member 303 within theupper frame member 204 in this order, the lower frame member 202 isfitted and secured in the thin-walled portion. Leakage of light from thelight emitting apparatus can be minimized by assembling in this way.

[0116] Since the pointer according to the present invention is free fromleakage of light due to such a construction as shown in FIG. 9, only thelight from the light observing plane 704 that provides high brightnessand satisfactory color-blended light can be observed.

[0117] (Embodiment 9)

[0118]FIG. 15 is a sectional view of the light emitting apparatus of thepresent invention used as the backlight of a TFT liquid crystal display.FIG. 16 is a plan view of the backlight when viewed on the lightemission observing plane side. As shown in FIG. 15, a plurality of firstlight emitting diodes 312 and second light emitting diodes are disposedin rows on the substrate 103. In addition, a diffusion sheet 713, a BEFsheet 712, a BEF sheet 707 and an LCD 706 are placed in this order onthe principal plane of the light guiding member, and a reflector sheet705 is provided on the surface opposing the principal plane. The lightemitting apparatus is made similarly to the previous embodiments exceptfor the variation described above.

[0119] Use of the present invention in the backlight makes it possibleto made a display that provides high brightness and satisfactorycolor-blended light.

[0120] (Embodiment 10)

[0121]FIG. 17 is a schematic sectional view of the light emittingapparatus according to this embodiment. A pointer is made according tothe present invention similarly to the tenth embodiment except forproviding an overhang 708 above the cover 201. Light can be preventedfrom leaking from the light guiding member 301 at the distal end of thepointer, by providing the overhang 708 at the distance end of the cover201. As a result, when the pointer according to this embodiment is used,only the light from the light observing plane 704 that provides highbrightness and satisfactory color-blended light can be observed.

[0122] (Embodiment 11)

[0123]FIG. 18 is a schematic sectional view of the light emittingapparatus according to this embodiment. A pointer is made according tothe present invention similarly to the tenth embodiment except forproviding a resin 709 below the lower frame member 202 at the distal endof the pointer. For the resin in this embodiment, the resin describedpreviously is used. Light can be prevented from leaking from the lightguiding member 301 at the distal end of the pointer, by providing theresin 709. As a result, when the pointer according to this embodiment isused, only the light from the light observing plane 704 that provideshigh brightness and satisfactory color-blended light can be observed.

[0124] (Embodiment 12)

[0125]FIG. 20 is a schematic plan view of the light emitting apparatusof this embodiment when viewed on the light emission observing planeside. FIG. 19 is a sectional view of the light emitting apparatus ofthis embodiment with cutaway showing the second light emitting diode322. A part of the end of the light guiding member 301 protrudes with afirst light introducing portion and a second light introducing portionsimilar to those of the first embodiment being formed thereon. The firstlight emitting diode 312 and the second light emitting diode 322 aremounted on one surface of the substrate 103 in a staggered arrangementso as to correspond to the first light introducing portion and thesecond light introducing portion, respectively. The light emittingdiodes 312 and 322 may have the same sizes. The substrate 103 is placedon the frame member on the side opposite to the light emission observingplane in parallel to the light emission observing plane.

[0126] By making the light emitting apparatus in such a construction asthe light introducing portions of the plurality of light emitting diodes312, 322 through which light is introduced into the light guiding member301 have such a step as in this embodiment, such a light emittingapparatus can be made that is capable of both satisfactorily blendinglight color and emitting light with high brightness and can be made verysmall. Also because the substrate is placed on the shaft side of thepointer, heat dissipation performance of the light emitting apparatuscan be improved.

[0127] (Embodiment 13)

[0128]FIG. 22 is a schematic plan view of the light emitting apparatusof this embodiment when viewed on the light emission observing planeside. FIG. 21 is a sectional view of the light emitting apparatus ofthis embodiment with cutaway showing the second light emitting diode922. The first light emitting diode 312 that is hidden in view by thesubstrate 103 is indicated with dashed line. A part of the end of thelight guiding member 101 protrudes with a first light introducingportion and a second light introducing portion similar to those of thefirst embodiment being formed thereon. The first light emitting diode312 and the second light emitting diode 322 are mounted on both surfacesof the substrate 103 in a staggered arrangement so as to correspond tothe first light introducing portion and the second light introducingportion, respectively. The light emitting diodes 312 and 322 may havethe same sizes. The substrate 103 is placed on the frame member on theside opposite to the light emission observing plane, perpendicularly tothe light emission observing plane.

[0129] By making the light emitting apparatus in such a construction asthe light introducing portions of the plurality of light emitting diodes312, 322 through which light is introduced into the light guiding member301 have such a step as in this embodiment, such a light emittingapparatus can be made that is capable of both satisfactorily blendinglight colors and emitting light with high brightness and can be madevery small.

[0130] (Embodiment 14)

[0131]FIG. 24 is a schematic plan view of the light emitting apparatusof this embodiment when viewed on the light emission observing planeside. FIG. 23 is a sectional view of the light emitting apparatus ofthis embodiment when viewed sideways. The first light emitting diode 312that is hidden in view by the substrate is indicated with dashed line. Apart of the end of the light guiding member 301 protrudes with a firstlight introducing portion and a second light introducing portion similarto those of the first embodiment being formed thereon. The first lightemitting diode 312 and the second light emitting diode 322 are mountedon both surfaces of the substrate 103 in a staggered arrangement so asto correspond to the first light introducing portion and the secondlight introducing portion, respectively. The light emitting diodes 312and 322 may have the same sizes. The substrate 103 is placed on thesurface of the protruding end in parallel to the light emissionobserving plane.

[0132] By making the light emitting apparatus in such a construction asthe light introducing portions of the plurality of light emitting diodes312, 322 through which light is introduced into the light guiding member301 have such a step as in this embodiment, such a light emittingapparatus can be made that is capable of both satisfactorily blendinglight color and emitting light with high brightness and can be made verysmall.

[0133] (Embodiment 15)

[0134]FIG. 25 shows circuit components 711 such as resistors, diodes andICs mounted on the substrate 103 together with the light emitting diodes312, 322.

[0135]FIG. 27A is a plan view showing a circuit pattern used for thelight emitting apparatus in another embodiment, and FIG. 27B is a sideview thereof. Leads of the light emitting diodes 312, 322 are connectedto electrically conductive pattern provided on the substrate 103 bysoldering. The substrate 103 also has a resistor 263 and a protectivediode 264 mounted thereon. Such a constitution makes it possible toeffectively use the space on the substrate 103, thereby making the lightemitting apparatus that is extremely small in size.

INDUSTRIAL APPLICABILITY

[0136] The present invention makes it possible to make a light emittingapparatus that is capable of both satisfactorily blending light colorsand emitting light with high brightness and can be made very small, byforming a step on the light introducing portions for the plurality oflight emitting diodes through which light is introduced into the lightguiding member.

1. A light emitting apparatus comprising: a light guiding member thatprojects light, that is incident on an end face thereof, through aprincipal plane; and a plurality of light emitting diodes that areoptically coupled with the end face, wherein the light guiding memberhas a protruding surface formed in part of the end face thereof andcomprises a first light introducing portion that is formed on theprotruding surface and is optically coupled to a first light emittingdiode, and a second light introducing portion that is optically coupledto a second light emitting diode and is formed on the rest of the endface.
 2. The light emitting apparatus according to claim 1, wherein thelight guiding member has a part of surface protruding on the side of theprincipal plane that emits light or on the side opposing the principalplane.
 3. The light emitting apparatus according to claim 1 or 2,wherein the first light emitting diode and the second light emittingdiode are surface-mounted light emitting diodes with light emittingportion of the first light emitting diode being higher than that of thesecond light emitting diode.
 4. A light emitting apparatus comprising: alight guiding member that has a distal end, an end face opposing thedistal end, and a principal plane located between the former two so asto project the light incident on the end face through the principalplane; and at least first and second light emitting diodes opticallyconnected to the end face of the light guiding member, wherein the endface of the light guiding member is made in such a structure that theoptical path over which light propagates through the light guidingmember is different depending on which of the light emitting diodes thelight is emitted.
 5. The light emitting apparatus according to claim 4,wherein the light guiding member has a shape of plate having the endface and an end face opposing the former end face, while the end face ofthe light guiding member has two portions corresponding to the first andsecond light emitting diodes with the optical path between the first endface portion and the end face is made longer than the optical pathbetween the other end face portion and the end face.
 6. The lightemitting apparatus according to claim 4 or 5, wherein the end face ofthe light guiding member is made in a stepped structure having such aprotruding surface as the one end face portion protrudes beyond theaxial direction of the light guiding member with respect to the otherend face portion.
 7. The light emitting apparatus according to claim 6,wherein the stepped structure of the light guiding member is disposed ina direction perpendicular or parallel to the axial direction between thedistal end and the end face of the light guiding member.
 8. The lightemitting apparatus according to any one of claims 1, 6 and 7, whereinthe protruding surface of the light guiding member is located outsidethe visible region of the light guiding member.
 9. The light emittingapparatus according to any one of claims 1, 2, 4, 7 and 8, wherein thefirst and second light emitting diodes are capable of emittingcolor-blended light having two or more peaks in the spectrum.
 10. Thelight emitting apparatus according to any one of claims 1 to 8, whereinthe light emitting apparatus is an instrument meter pointer.
 11. Thelight emitting apparatus according to any one of claims 1 to 8, whereinthe light emitting apparatus has a substrate whereon the light emittingdiode and circuit elements are mounted.
 12. A vehicle instrument paneldisplay comprising the light emitting apparatus of any one of claims 1to 11 as a meter pointer of an instrument panel installed in a vehicle.